you made a plan for shopping on sunday (07 Jan) 1 pm-7pm .so shopping is your project and you have made project management plan for shopping like :scope as 3 Gowns(Plan scope mngmt) budget as 9k (Plan cost mngmt) thinking 3 k per gowntime as 6 hrs (Plan schedule mngmt) thinking 2 hrs per gown

project (shopping) has started so execution has started and at 3 pm you want to see what and all things done or not done (monitor & control). so your:

work performance data says: 1 gown bought, 8k spent

work performance information says: cost variance is high bcoz instead of 3k per gown you have already spent 8k on one, schedule and scope going as per plan.

work performance report says:project is overbudget but on track in terms of schedule, 33% scope delivered

now you need to change your plan ( like increase initially planned overall budget of 9k to 24k) documented in PMP and come up with a modification in your intial plan so its kinda iterative process .. hence is work performance report needed to develop the PMP..